Resilient floor coverings can be formed into sheets or individual tiles. Typically, in the manufacture of a resilient floor covering, a wear layer is combined with a substrate and resin to form the resilient sheet or tile. The substrate usually comprises a felted or matted fibrous sheet of overlapping, intertwined filaments or fibers. To the substrate is typically applied a substantially uniform layer of a liquid or semi-liquid resinous composition containing a synthetic polymeric material, usually an ungelled polyvinyl chloride plastisol and a blowing or foaming agent. The liquid or semi-liquid plastisol vinyl resin composition is subsequently firmed or gelled at an elevated temperature. This gelled plastisol may be printed with a decorative pattern or design having a blowing or foaming inhibitor for chemically embossing the substrate.
A wear layer is often applied to the surface of the polyvinyl chloride plastisol disposed on the substrate. Generally, the wear layer consists of a transparent layer that imparts resistance to puncture. These typically consist of a layer of transparent polyvinyl chloride, but urethane and urethane acrylates have been utilized. Additionally, there may also be applied another transparent topcoat layer that improves the stain and scratch resistance of the composite's surface. Examples of such wear layer composites can be found in U.S. Pat. Nos. 4,333,987, 4,180,615, 4,393,187 and 4,507,188.
A wear layer is any layer which improves the performance of the floor covering, such as an improved gouge, tear and rip resistance, improved stain resistance, or improved scratch resistance. A topcoat is a wear layer that has at least a portion that forms the exposed surface of the floor covering. A high performance wear layer or topcoat is a generally thin (less than about 3 mils) wear layer or topcoat formed from a radiation, e.g. ultraviolet (UV) or electron beam (EB), cured composition.
High performance wear layers or topcoats are cured by radiation to enhance their durability and finish. Radiation curable coatings are typically cured by exposure to ionizing irradiation or ultraviolet light. Such coatings are known in the art; for example, urethane coatings cured with ultraviolet light to provide protective wear layers for wall or floor tiles are described in U.S. Pat. No. 4,180,615. Additionally, in U.S. Pat. No. 3,918,393, there is described a method for obtaining a non-glossy coating on various substrates by curing radiation sensitive material with ionizing irradiation or ultraviolet light in two stages. In this process, the coating is partially cured in an oxygen-containing atmosphere and later completed in an inert atmosphere. In each of the above examples, the wear layer is unpigmented.
Unfortunately, radiation curable wear layers and topcoats are subject to substantial difficulties when coloring is added. Coloring is added by the addition of various pigments to the wear layer. The incorporation of pigment, especially enough pigment to make the coating opaque, produces a coating which is hard to cure and therefore reduces durability. There are no known floor coverings that include a pigmented high performance topcoat or a pigmented high performance wear layer which is covered by a high performance topcoat. Thus, there is a need for a pigmented high performance topcoat or a combination of a pigmented high performance wear layer/high performance topcoat on the up areas of an embossed floor covering having a sufficient durability to function on a decorative floor covering.